Production of combustible gas from comminuted solid carbonaceous material



Dec. 20, 1955 F A w LEFFER 2,727,812

PRODUCTION OF CMBfJSTIBLE GAS FROM COMMINUTED SOLID CARBONACEOUS MATERIAL Filed May 31, 1951 COMMINUTED CARBONACEOUS HOT COMBUSTABLE souo CHARGE GAS v I 2 T/ GAS PRODUCING ZONE (REDUCING) /4 t '3 SUPERHEATED M ExcEss STEAM TEA w? s M COZGCO-CONTAINING 0 A T 6 :2 T FREE COMBUSTION eAsEs 53 54 f 52 HEATING ZONE T' (OXIDIZING) 56 55 STEAM SUPERHEATING T ZONE\ 48 IO ExcEss eAs HEATED PARTICLE 2| 4s STEAM RECYCLE COMBUSTION 3A5 GENERATING l9 n +WITH FREE 0 ZONE 1 CONTENT FINAL BURNING was f o -eAs 2 COOLED COMBUSTIBLE' 0 GAS PREHEAT- GAS 22 23 Ame ZONE CARBON- FREE X HOT ASH 26 d LOW PRESSURE quENcHme 37 OXYGEN GAS WASTE STEAM AND/ ZONE 0R CONDENSED 56 4 WATER.

s2 27 u 25 28 g WATEF7 INVENTUQI l FREDERICK A. W. LEFFER SLURRY BY: CM f.

ATTOR YS:

United States Patent *O "ice 2,727,812 PRODUCTIUN or eoMsUsTIBLE GAS 1 FROM coMMiNuran soup CARBONACEOUS MA- TERIAL Frederick A. W. Letter, Riverside, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application May 31, 1951, Serial No. 229,231

5 Claims. (Cl. 48-197) This invention relates to an improved method for continuously producing a combustible gas from comminuted solid carbonaceous material, and particularly to a continuous operation having coked and carbonized solid particles maintained in cyclic circulation through a gas producing zone and a heating zone.

Various methods have been used for producing'water ing. The carbonaceous solid'materials are in general of low cost, however, the gas producing system must also be of a nature providing a low cost combustible gas in order that resulting synthetic hydrocarbon materials may compete with corresponding products produced in'present day practice from mineral oil sources. g

It is a principal feature and object of the present invention to produce a combustible 'gas at an overall low cost by improved heat utilization and thermal efiiciency, with residual and unreacted carbon from the solid charge'material being burned and exhaustively utilized in 'a manner providing heat for the gas producing step itself.

In a broad aspect, the present invention provides an improved method for producing a combustible gas from solid carbonaceous material, in a manner which comprises, passing a comminuted solid carbonaceous'charge stream into the cyclic flow path of hot residual solid carbonaceous particles maintained in continuous circulation through a confined gas producing zone and a confined particle heating zone, introducing a hot gasiform mixture containing mainly carbon dioxide and steam into contact with the carbonaceous particles within the gas producing zone at a reaction temperature producing a' combustible gas comprising carbon monoxide and hydrogen,'withdrawing resulting combustible gas from the gas producing zone while continuously passing contacted particles 'th'erefroin to the heating zone, introducinganoxidizing gas stream into contact with the particles in theheatingzone and incompletely burning ca'rbontherefrom at'a temperature substantially above the reaction temperature maintained within the gas producing zone and forming thereby acombustion gas substantially devoid of free-oxygen, continuously withdrawing the heated residual carbon-containing particles from the heating zone and diverting a portion thereof from the cyclic flow path into a separa'te'confined burning zone, contacting the particles in the separate burning zone with a gaseous stream having'an excess of free oxygen and therein burning substantially completely the carbon from the particles, passing a resulting "hot j'gas stream containing combustion gases and free oxygen from the burning zone into contact with the particles in the 2,727,812 Patented Dec. 20, 1955 heating zone, and continuously discharging a stream of hot' combustion gases'substantially devoid of free oxygen from the heating zone and combining it with superheated steam-thereby providing the aforesaid hot gasiform mixture being continuously introduced into contact with the particles in the gas producing zone.

In another aspect, the present invention also provides an improved method for producing combustible gas which comprises introducing astream of comminuted solid carbonaceous material into the cyclic flow path of hot residual solid carbonaceous particles maintained in continuous' circulation through a confined gas producing zone and a confined particle heating zone,'reacting carbon on the particles in the gas producing zone with a gasiform mixture containing mainly carbon dioxide and steam'and being substantially devoid of free oxygen thereby forming a hot combustible gas comprising carbon monoxide and hydrogen, burning carbon from the particles in the heating zone by contact with an oxidizing gas of controlled free-oxygen content at a temperature substantially above the reaction temperature maintained in the gas producing t zone to form a combustion gas substantially devoid of free oxygen, introducing resultant combustion gas substantially-at the temperature of its formation from the particle heating zone into the gas producing zone thereby supplying to the latter a substantial portion of the heat required-for the endothermic reaction therein, passing heated particles from the particle heating zone in the cyclic flow path into the gas producing'zone at a rate at which the remaining portion of the aforesaid heat requirement is supplied thereto, withdrawing the hot combustible gas from the-gas producing zone into a confined heat exchanging zone and therethrough in indirect heat exchange with low temperature aqueous fluid which is thereby transformed into superheated steam, and introducing resultant superheated steam from the heat exchanging zone continuously into the gas producing zone.

, In accordance with the present invention, heat is supplied to the gas producing zone by the continuous stream of heatedcok'ed and carbonized particles passing from the heating zone to the gas producing zone, as well as by the continuously supplied gasiform mixture comprising primarily carbon dioxide and superheated steam. With a temperature of'the order of 1600 to 1850 F., or slightly higher, in'the gas producing zone, there are effected in this zone a carbon dioxide reducing reaction and a carbon-steam reaction with the formation of a desirable ncombustible gas stream comprising primarily carbon monoxide'and hydrogen, carbon on the particles in the gas producing zone participating in both of these reactions. The comminuted charged material is preferably introduced into the cyclic flow path of hot residual solid carbonaceous particles at the gas producing zone, however, the major portion of the solid charge material is passed into the gas producing zone only in those operations where it is the product of a separate high temperature or'low temperature coking'operation, or acarbonized material. Where the charge 'is 'primarily'an uncoked orjuncarbonized solid hydrocarbonaceous material, it is preferablyintroduced directly into the heating zone or into the stream of residual carbonaceous-particles passing from the gas producing zone into'the heating zone so that at leasta "major-portion of such charge undergoes carbonization and coking in the heating zone prior to entering the gas producing 'zone.

' It is not intended to limit the present invention to any one means of transporting the solid material for maintaining the continuous cyclic flow path of solid particles through the :gas producing zone'and the heating zone. The solid carbonaceous material may be continuously transported from one zone to another by fluidization, or alternatively, the particles may pass in part by gravity flow and in part by fiuidization or gas lift transporting so that there is a continuous non-mechanical movemen and circulation of particles from one contacting zone to another.

It is a particular feature of the present invention also to maintain the oxidative reactions within the heating zone under controlled conditions yielding a coked and carbonized solid carbonaceous material suitable for providing the desired gas producing reaction.within the sepa rate gas producing zone. The oxidizing gas stream introduced into the heating zone of course provides some free oxygen to permit burning and coking of the particles within the bed thereof, as well as to provide heat absorption by the particles so that they may transfer heat to the gas producing zone. However, oxidation and combustion of the solid carbonaceous material is incomplete within the heating zone and resulting heated carbonized particles are continuously discharged and passed to the gas producing zone to supply at least a substantial part of the endothermic heat requirements of the gas producing zone. in view of the incomplete combustion within the heating zone a resulting stream of high temperature combustion gas substantially devoid of free oxygen is discharged continuously from the heating zone. The latter gas stream, in which the content of the carbon dioxide appreciably exceeds that of carbon monoxide, is subsequently mixed with high temperature superheated steam to provide a desirable high temperature stream mainly composed of CO2 and steam whereby to efiect the desired combustible gas producing reaction within the gas generating zone. A maximum conversion of carbon dioxide to carbon monoxide is made possible in the gas producing zone by substantially excluding from this zone free oxygen which would foster the far more rapid reverse reactions of oxidation of carbon and carbon monoxide to carbon dioxide. The charge gas stream to the gas producing zone by reason of its high temperature also furnishes a substantial portion of the endothermic heat requirements for the combustible gas producing reaction. in the preferred mode of operation, the entire endothermic reaction heat requirement of the gas producing zone is furnished solely by the sensible heat contents of this gas charge stream and the heated particle stream supplied in the cyclic flow path from the particle heating zone to the gas producing zone in such manner that the heat contained in the hot gas charge stream is supplemented to the required extent by controlling the rate of supply of heated particles in substantially uncooled condition from the particle heating zone to the gas producing zone.

it is also a feature of the present invention to continuously divert a portion of the carbonized or residual carbon-containing particles from the cyclic fiow path by withdrawing such portion from the heating zone and passing it to a final burning zone wherein the residual carbonaceous matter is substantially completely burned from the particles in the presence of an oxidizing gas stream having an excess of free oxygen. The resulting hot gaseous stream issuing from the final burning zone then contains some free oxygen in admixture With combustion or flue gases, and this hot mixture is passed, at least in part, to the heating zone. Thus, there is supplied to the heating zone a high temperature gaseous stream which provides at least a substantial portion, or preferably the entire amount, of the free oxygen required for effecting the incomplete burning within the heating zone. in addition to providing high temperature gas for introduction into the heating zone, the substantially complete burning of carbonaceous matter from the particles in the final burning zone provides heat for auxiliary steam production and for preheating of the air or oxygencontaining streams. Thus, the heated incombustible residue or ash material from the final burning zone may be passed to a quenching zone and therein contacted' with an aqueous stream to produce auxiliary steam which may be used in part or all to advantage for the driving of pumps and the like, but which preferably is used, at least in part, for indirect heat exchange with the air or oxygen stream to provide preheating of the latter for introduction into the final burning zone and into the heating zone. This exhaustive utilization of the carbon content of the solid charge thus provides a high thermal efiiciency for the entire process.

In a preferable operation, the superheating of the steam which is to be admixed with the hot combustion gases from the heating zone to provide the hot carbon dioxide and steam mixture for introduction into the gas producing zone is effected by indirect heat exchange of water or low temperature steam with the hot combustible gas stream passing from the gas producing zone. This indirect heat exchange may be accomplished in various ways, as for example, tubular heat exchangers may be used for the indirect. heat exchange passage, or a pebble heater arrangemerit may be utilized, having a heat retentive granular or spheroidal inert solid in circulation through a heat ab sorption zone and a heat dissipating zone, with the hot combustible gas stream from the gas producing zone being passed countercurrently through the heat retentive solid material in the heat absorbing zone, and low temperature steam or water and resultant low temperature steam passed countercurrently through the solid material in the heat dissipating zone.

The free oxygen-containing oxidizing gas which is introduced into the final burning zone, and, if desired, also into the particle heating zone may be air or a gas of higher free oxygen content, such as commercial oxygen or a mixture thereof with air. The oxygen gas is selected primarily with regard to the calorific value or composition of the combustible gas desired as the final combustible gas product. The use of commercial oxygen or an oxygen-air mixture aids in keeping the nitrogen concentration to a minimum within the combustible product gas.

Reference to the accompanying drawing and the following description thereof will serve to better illustrate the present continuous gas producing operation as well as various advantageous features thereof.

Referring now to the drawing, there is indicated a charge line 1 having valve 2 which provides means for introducing a comminuted carbonaceous solid charge material to gas producing zone 3. Alternatively, all or a portion of the comminuted solid charge may pass by way of line 4, valve 5, and through line 6 into the confined heating zone 7. The solid charge may be supplied in any suitable state of comminution which ordinarily ranges from 4 to 200 mesh per linear inch, but may be as large as in the case of compact moving bed type of operations, and preferably is of about 50100 mesh, particularly where fluidized particle transfer between some of the contacting zones is employed. Where the charge material is low temperature carbonization coke, petroleum coke, or a high temperature coke, or other carbonaceous material having a high carbon content and a relatively low volatile hydrocarbon content, the material is passed preferably through line 1 directly into the gas producing zone 3, however, if the solid charge material is uncoked or uncarbonized solid hydrocarbonaceous material it is preferably charged into the heating zone 7 so that it 'may undergo carbonization concomitantly with controlled incomplete combustion within heating zone 7 and be subsequently recycled in carbonized and heated state to the gas producing zone. A continuous cyclic flow path of subdivided solid carbonaceous material is main tained from the gas producing zone 3 by Way of line 6 and control valve 8 to the heating zone 7, and from the latter zone by way of line 9 and control valve it to the gas producing zone 3. The temperature and quantity of highly heated particles passing from heating Zone '7 by way of line 9 to the gas producing zone 3, are so controlled that at least a substantial portion, and more advantageouslya major portion, of the endothermic heat required for the reducing andcombustible gas producing reaction within zone 3 issupplied by the continuous stream of highly heated residual carbon-containing particles.

A desired combustible gas is produced continuously Within zone 3 by introducing into contact with the heated and carbonized solid particles therein a gas mixture comprising hot'combustion gases from heating zone 7 and passing by Way of line '11 having control valve 12, and high temperature superheated steam from line 13 having control valve 14. Thus, a gaseous stream having a large proportion of carbon dioxide and superheated steam and being substantially devoid of free oxygen is introduced into zone 3 wherein a portion of the carbon on the particles present'participates in a carbon dioxide reducing reaction and a steam-carbon reaction at a temperature maintained at the order of 1600 to 1850 F. or more, to form a high temperature combustible gas being continuously discharged by way of line 15 and valve 16.

In the heating zone 7, a portion of the carbon content of the charge particles 'is'burned by'means of an oxidizing gas stream introduced by 'way of line 17 and control valve 18; the free oxygen content of this oxidizing gas stream is controlled to'impart to'the solid particles with in heating zone 7 a temperature substantially higher than that maintained in the gas producing zone 3. The particles within zone 7 may thus be heated to temperatures of at least about 1800 and preferably within the approximate range of from 2000 to 2400 F.; this temperature is most advantageously maintained in the neighborhood of from 2200 to 2250F., depending upon the fusion or agglomeration characteristics of the particular comminuted material. By control of the oxygen content of the oxidizing gas stream, the combustion is controlled so that the highly heated particles issuing from the heating zone 7 and passing by way of line 9 to gas producing zone 3 have a desired residual carbon content. In a preferred operation, a major portion of the heat requirement of the gas producing zone is furnished thereto by'the hot cycle stream of particles passing 'by'way'of 'line 9 to zone 3, while the remaining minor portion of "the 'heat requirements for zone 3is supplied by the hot gaseous stream being introduced by way of line 11.

The total heat generation in the heating zone Tand the amount of heat supplied by the particlesaridgas therefrom to the gas producing zone 3 is kept at a minimum by virtue of a'substantial'am'ount of heat recovered in the process by high temperature superheated steam which is introduced into contact and admixture with the combustion gases in line 11. The superheated steam is produced by indirect heat exchange with'the hot product stream from line 15. The combustion gas stream principally containing carbon dioxide and carbon'monoxide and being discharged from the heating zone 7 for subsequent introduction into-the gas producing zone 3 is a gas stream substantially devoid of free oxygen-in view of the incomplete burning and oxidation effected within the bed of material of zone 7. The oxidizing gas stream entering the heating zone 7 by way of line 17, however, is normally a combustion gas stream containing free oxygen that is unused in the final burning Zion e 19 by reason of the latter zone having an excess of air or oxygen charged thereto.

In order to provide a process of high thermal efiiciency as well as to eliminate ash constituents from the processing unit at practically the samerate at which they are introduced into the system by the carbonaceous or hydrocarbonaceous charge material, a continuous stream of residual particles is diverted from the cyclic particle flow path by withdrawing such stream from heating zone 7 by way of line 20 and valve 21 and introducing it into the final buning zone 19. The portion of residual particles thus diverted to the final burning zone is normally a minor portion oft'he total quantity of heated carboncontaining particles being discharged from the heating zone, the major portion thereof being directed from the heating zone 7 to the gas roducingzone 3.

In the burning zone 19, the carbon content of the particles supplied thereto is burned substantially completely with the aid of air'or an oxygen-containing stream supplied through line 22 and valve 23. In accordance with the preferred operation of the present invention, the oxidizing gas stream entering zone 19 by Way of line 22 has a substantial excess of free oxygen so that the resulting combustion gas stream still contains suflicient free oxygen for passage by way of line 17 to the heating zone, in order to effect the desired incomplete combustion in that zone. It is also desirable that the burningof the residual carbonaceous matter from the particles in the final burning zone 19 is regulated so that ash fusion or clinkering will be substantially precluded. In general, the combustion temperature in zone '19 is maintained higher than the reaction temperature in thegas producing zone 3. When the carbonaceous solid charge material entering through line 1 yields ash of relatively low fusion point, the temperature of combustion in the final burning zone may be lower than that in the heating zone 7, while with ash of high fusion point the combustion in zone 19 may be effected at about the same or even a higher temperature than that in zone 7. In any event, the combustion temperature in the final burning zone is maintained about 50 -75 F. below the ash fusion temperature and is readily controlled by the regulation of the temperature of the oxygen-containing stream supplied through line 22 and, if desired, also by recirculation of combustion gas upon removal thereof through lines 17 and 42 and then through a heat recovery device (not shown), wherein it iscooled to the required extent.

The substantially carbon-free hot ash from the final burning zone 19 is continuously passed by way of line 24 and valve 25 to an ash quenching zone 26 wherein residual heat maybe taken up by contact with an aqueous stream in the production of auxiliary or low pressure steam. In the present embodiment, water is pumped by way of the pump 27, line 28, and valve 29 into the quenching zone 26 so that there is direct contact quenching of the ash material in the latterzone .to provide low pressure steam being discharged by way of line 30 to preheating zone 31. Resulting cooled ash, in slurry form, is continuously withdrawn from the lower endof the quenching zone 26 by way of line 32 and valve 33. Thus, substantially all of the'ash formedin the final burning zone is effectively .pre cluded from gaining access to the cyclic flow path of residual carbon-containing particles.

The low pressure steam passed to the heating chamber 31 is used to advantage in this instance to preheat the air or oxygen gas stream which is passed to the final burning zone 19 and to the heating zone 7, however, part 'or all of the low pressure steam may be used advantageously for other auxiliary purposes, such as the driving of blowers, and pumps of the system or other remaining steam requirements of the process. Air or other free oxygen containing gas is passed by Way of line 34, valve 35, and pump 36 to line 37 connecting with the preheating chamber 31 in order that the oxygen stream may pass in indirect heat exchange relationship with the steam being passed from the quenching zone 26. This arrangement permits 'a preheated ,air or oxidizing, gas stream to be discharged 'by way of, line 38 to line 22 connecting with the final burning 'zone 19 or alternatively by Way of valve 39 and line 38 to, the line 17 connecting directly vvith the heating zone 7. 'Resulting low pressure waste steam or condensed water is discharged from the preheating zone 31 by way of line 40 and valve 41.

Normally, the free oxygen-containing oxidizing gas stream which is utilized in the final burning zone 19 as well as in the heating zone 7 is preheated satisfactorily by the heat exchange with the low pressure steam in heat exchange zone 31, however, where it may be found desir able to have a still higher temperature oxidizing gas stream, then additional heat exchange may be utilized as for example, by passing excess combustion gas from the final burning zone in heat exchange relationship with the oxygen containing gas stream. Although means for this latter heat exchange are not indicated in the drawing, excess combustion gas may be discharged from the final burning zone 19 by way of line 17 and outlet line 42 having control valve 43 and may be directed to such heat exchange means. Also, excess combustion gas from the heating zone 7 which may be discharged by way of line 12 and line 55 having valve 56, may be utilized in suitable heat exchange apparatus for preheating purposes.

As, hereinbefore noted, the oxygen concentration of the oxygen gas stream may be selected primarily with regard to the calorific value or composition of the combustible gas desired as a final product from the reducing and gas producing zone 3. Commercial oxygen or an oxygen-air mixture of higher free oxygen content than air, may be utilized where it is desired to keep the nitrogen concentration to a minimum in the combustible prod hot gas stream. Normally a sufficient quantity of oxidizing gas stream may be passed through the final burning zone 19 to provide a resulting gas stream with excess free oxygen and at the same time provide a desirable high temperature gas stream suitable to effect oxidation of the desired portion of the carbonaceous matter from the solid particles within heating zone 7. However, whenever the excess free oxygen in the combustion gas issuing from the final burning zone 19 is insufficient for the controlled incomplete combustion in the heating zone 7, oxygen gas is added in the required amount to the stream of hot combustion gas being supplied from the final burning zone 19 to the heating zone, with the additional oxygen being introduced by way of line 38 and valve 39 to line 17. Ordinarily, the concentration of free oxygen in the total gas mixture introduced into the particle heating zone 7 is less than that of air, even in those cases where commercial oxygen or an oxygen-air mixture of higher oxygen content than air is the gas supplied to the process.

The high temperature superheated steam which is passed in admixture with the CO2 containing stream into the reducing and gas producing zone 3, is in a preferred operation provided by passing an aqueous stream in heat exchange relationship with the hot combustible gas stream being produced in the process. in the present embodiment, water is supplied from line 23 and line 44 having control valve 4-5 to a steam generating zone 4-6 wherein it passes in indirect heat exchange relationship with partially cooled combustible gas being passed by way of .line 47 from the steam superheating zone 48. The latter zone in turn is supplied with high temperature combustible product gas from line 15. The cooled product stream from the steam generating zone 46 is discharged therefrom by way of line 49 and control valve 54), while steam is passed into the steam superheating zone 48 by way of line 51. By indirect heat transfer from the combustible gas stream, high temperature superheated steam is produced in the superheating zone 48 and discharged therefrom by Way of line 52 into line 13 communicating with line 11 and the gas producing zone 3. The generation and superheating of steam in the zones 46 and 4-8 is readily eitected at a steam pressure independent of the pressure on the auxiliary steam generated in the quench ing zone and higher than the pressure maintained in the cyclic particle flow path, the final burning zone, and the quenching zone, so that the resultant high temperature, high pressure superheated steam can be introduced directly (without any intervening compression) into the gas producing zone and its rate of supply to the latter zone is readily controlled by means of valve 14 in line 13. Excess high pressure superheated steam, which is not needed in the gas producing zone 3 may be discharged from the unit by way of line 53 and valve 54.

The gas producing zone 3, the particle heating zone 7,

the final burning zone 19 and the ash quenching zone 26 are advantageously maintained at approximately the same pressure, the pressure differentials between any two of these zones being merely that required to maintain the desired flow of materials within the system. Such general pressure level may range from subatmospheric to 200 p. s. i., or higher, and preferably is at least sufliciently above atmospheric pressure to permit controlled gas discharge from the system without the aid of vacuum or exhaust pumps. Pressures of from 50 to 75 p. s. i. in the contacting zones 3, 7, 19 and 26 generally permit an optimum operation from the point of view of overall efficiency. The pressure on the steam sides of the high pressure steam generating zone 46 and superheating zone 4-8 normally is maintained from about 20 to about 50 p. s. i. higher than the pressure in the gas producing Zone 3.

Various modifications may be made in this improved combustible gas producing operation, within the scope of the present invention. For example, the flow of the solids charge and the continuous transfer of particles between zones may be maintained by mechanical transporting means or alternatively by gravity flow and fluidized lift means. A superimposed relationship of zones may be utilized to permit gravity flow of solid particles from the gas producing zone to the heating zone, or vice versa, and gravity flow from the heating zone to a final burning zone, and/ or from the latter to the quenching zone. It is of course a principal feature of the present improved operation to maintain a continuous cyclic flow path for the solids material through the gas producing zone 3 and the heating zone 7; thus, where a superimposed relationship is utilized it is necessary to provide mechanical or preferably gas lift means for moving the solids material from the lower-most zone to the upper zone. In a fluidized lift operation, a gaseous charge stream to a given zone may be utilized to advantage to eifect the fluidization and lifting of the particles to that zone. For example, the oxidizing gas stream may be utilized to pass contacted particles from the gas producing zone, where the latter is a lowermost zone, to an elevated heating zone. Alternatively, the mixed stream of carbon dioxide and superheated steam may be utilized to fiuidize and transport contacted particles from the particle heating zone to the gas producing zone, where the latter is the uppermost zone.

Within each of the contacting zones, the gaseous contacting streams preferably contact the solid particles in a counter-current flow, or in a fluidized concurrent flow so that there is adequate contacting of all of the solid particles within a given contacting zone by the gaseous stream being introduced thereto.

It is not intended to limit the present invention to any one form of indirect heat exchange relationship within the various heat utilization steps provided in combination with the improved process. In other words, various tubular types of heat exchangers may be utilized in the steam superheating and steam generating zones, or the well known pebble heater type of operation may be utilized to absorb heat'from the hot combustible product gas stream from the gas producing zone 3 and for dissipating heat to a low temperature steam or water stream being introduced into contact with the heat retentive solid material for the formation of the desired high temperature high pressure superheated steam which is utilized within the gas producing zone. 3

Although not shown in the present diagrammatic drawing, steam or other suitable stripping medium may be utilized for aerating or stripping the solid particles as they pass from one contacting zone to another so that solids compacting in transfer passageways of restricted cross-section is precluded and adsorbed or occluded gaseous materials'may be substantially stripped from the particles prior to their entering another confined zone, particularly where such occluded gaseous materials would be of a contaminating nature.

I claim as my invention:

1. A method for producing combustible gas from solid carbonaceous material which comprises introducing a stream of comminuted carbonaceous material and a recycle stream of hot carbonaceous particles into a confined gas producing zone and into contact therein with a hot gasiform mixture mainly composed of carbon dioxide and superheated steam at a carbon-steam reaction temperature and thereby forming a combustible gas comprising carbon monoxide and hydrogen, withdrawing said combustible gas from said gas producing zone while continuously discharging contacted carbon-containing particles from said gas producing zone into a separate confined heating zone, introducing a hot gas stream of controlled free oxygen content into said heating zone and effecting incomplete burning of carbon from the particles therein at a temperature substantially above said carbon-steam reaction temperature in a manner producing a hot combustion gas substantially devoid of free oxygen, continuously returning a stream of resulting heated residual carbon-containing particles from said heating zone as said recycle stream of hot particles to said gas producing zone and concomitantly passing another stream of said residual carbon-containing particles from said heating zone into a separate confined burning zone and therein burning the residual carbon substantially completely from the particles in the presence of a gaseous stream containing an excess of free oxygen, withdrawing a resulting hot combustion gas stream containing free oxygen from said burning zone and passing it into said heating zone as said hot gas stream of controlled free oxygen content, withdrawing a stream of said combustion gas substantially devoid of free oxygen from said heating zone and commingling it while still hot with highly superheated steam, introducing the thus commingled high temperature gaseous streams as said gasiform mixture mainly composed of carbon dioxide and superheated steam into contact with the particles in said gas producing zone, continuously withdrawing resulting hot ash particles from said burning zone and passing them in direct heat exchange with an aqueous stream of appreciably lower temperature and thereby cooling said ash particles and producing a separate stream of steam, and passing said separate stream of steam in indirect heat exchange relationship with an oxygen-containing gas stream being introduced to said burning zone.

2. The method of claim 1 further characterized in that said combustible gas is withdrawn in heated state from said gas producing zone and passed in indirect heat exchange with an aqueous stream in a manner producing high temperature superheated steam, and superheated steam thus produced is commingled with said stream of combustion gas substantially devoid of free oxygen to form said gasiform mixture mainly composed of carbon dioxide and superheated steam.

3. The method of claim 1 further characterized in that said comminuted solid carbonaceous material has a low volatile content and has been carbonized prior to its introduction into said gas producing zone.

4. The method of claim 1 further characterized inthat the initial solid carbonaceous charge comprises uncoked hydrocarbonaceous particles, and said particles are first introduced into said particle heating zone and therein carbonized before being passed therefrom into said gas producing zone together with residual carbon-containing particles which have passed at least once in cyclic flow through said heating and gas producing zones.

5. A method for producing a combustible gas from solid carbonaceous material, which comprises, introducing comminuted carbonaceous perticles into a cyclic flow path of hot residual solid carbonaceous particles maintained in continuous circulation through a confined gas producing zone and a confined particle heating zone, producing a combustible gas comprising carbon monoxide and hydrogen as principal normally gaseous components by interreacting a gasiform mixture containing mainly carbon dioxide and high temperature superheated steam in said confined gas producing zone and the solid carbonaceous particles therein at a reducing and gas producing temperature in the range of from about 1600 to about 1850 F., furnishing a major portion of the endothermic heat required for producing said combustible gas as sensible heat of the particles flowing in said cyclic flow path from said heating zone into said gas producing zone, providing the remaining portion of said endothermic heat requirement within said gas producing zone as sensible heat in said gasiform mixture being introduced into contact with the particles in said gas producing zone, continuously discharging said combustible gas from said gas producing zone while continuously passing contacted solid particles therefrom in said cyclic flow path into said heating zone, introducing a hot gas stream of controlled free oxygen content into said heating zone and efiecting the incomplete burning of carbon from the particles therein at a temperature within the range of from about 2000 to about 2400" F., continuously discharging the resulting hot combustion gas substantially devoid of free oxygen from said heating zone and admixing at least a portion thereof at substantially the temperature of its formation with superheated steam in a manner providing said gasiform mixture, continuously diverting a minor portion of the solid residual carbon-containing particles heated in said heating zone from the cyclic flow path thereof into a separate confined burning zone, introducing an oxidizing gas stream containing an excess of free oxygen into said confined burning zone and therein burning residual carbon substantially completely from said particles at a temperature above that maintained in said gas producing zone, passing a stream of hot resulting combustion gas containing free oxygen from said burning zone into said heating zone as saidhot gas stream of controlled free oxygen content, continuously discharging hot substantially carbon-free ash-like particles from said burning zone and passing them in direct contact with an aqueous stream in a confined quenching zone and therein producing steam, passing steam from said quenching zone in indirect heat exchange relationship with said oxidizing gas stream being introduced into said burning zone and thereby preheating said oxidizing gas stream, continuously passing a stream of said combustible gas substantially at the temperature of its withdrawal from said gas producing zone into indirect heat exchange relationship with an aqueous stream and thereby transforming the latter into high pressure high temperature superheated steam, and passing a stream; of the resulting superheated steam into admixture with; said hot combustion gas substantially devoid of oxygeri in a manner providing said gasiform mixture.

References Cited in the file of this patent UNITED STATES PATENTS 2,527,575 Roetheli Oct. 31, 1950 2,554,263 Nelson May 22, 1951 2,579,397 Roetheli Dec. 18, 1951 2,622,973 Barr Dec. 23, 1952 2,623,817 Lewis Dec. 30, 1952 

1. A METHOD FOR PRODUCING COMBUSTIBLE GAS FROM SOLID CARBONACEOUS MATERIAL WHICH COPMPRISES INTRODUCING A STREAM OF COMMINUTED CARBONACEOUS MATERIAL AND A RECYCLE STREAM OF HOT CARBONACEOUS PARTICLES INTO A CONFINED GAS PRODUCING ZONE AND INTO CONTACT THEREIN WITH A HOT GASIFORM MIXTURE MAINLY COMPOSED OF CARBON DIOXIDE AND SUPERHEATED STEAM AT A CARBON-STEAM REACTION TEMPERATURE AND THEREBY FORMING A COMBUSTIBLE GAS COMPRISING CARBON MONOXIDE AND HYDROGEN, WITHDRAWING SAID COMBUSTIBLE GAS FROM SAID GAS PRODUCING ZONE WHILE CONTINUOUSLY DISCHARGING CONTACTED CARBON-CONTAINING PARTICLES FROM SAID GAS PRODUCING ZONE INTO A SEPARATE CONFINED HEATING ZONE, INTRODUCING A HOT GAS STREAM OF CONTROLLED FREE OXYGEN CONTENT INTO SAID HEATING ZONE AND EFFECTING INCOMPLETE BURING OF CARBON FROM THE PARTICLES THEREIN AT A TEMPERATURE SUBSTANTIALLY ABOVE SAID CARBON-STEAM REACTION TEMPERATURE IN A MANNER PRODUCING A HOT COMBUSTION GAS SUBSTANTIALLY DEVOID OF FREE OXYGEN, CONTINUOUSLY RETURING A STEAM OF RESULTING HEATED RESIDUAL CARBON-CONTAINING PARTICLES FROM SAID HEATING ZONE AS SAID RECYCLE STREAM OF HOT PARTICLES TO SAID GAS PRODUCING ZONE AND CONCOMITANTLY PASSING ANOTHER STREAM OF SAID RESIDUAL CARBON-CONTAINING PARTICLES FROM SAID HEATING ZONE INTO A SEPARATE CONFINED BURNING ZONE AND THEREIN BURNING THE RESIDUAL CARBON SUBSTANTIALLY COMPLETELY FROM THE PARTICLES IN THE PRESENCE OF A GASEOUS STREAM CONTAINING AN EXCESS OF FREE OXYGEN, WITHDRAWING A RESULTING HOT COMBUSTION GAS STREAM CONTAINING FREE OXYGEN FROM SAID BURNING ZONE AND PASSING IT INTO SAID HEATING ZONE AS SAID HOT GAS STREAM OF CONTROLLED FREE OXYGEN CONTENT, WITHDRAWING A STREAM OF SAID COMBUSTION GAS SUBSTANTIALLY DEVOID OF FREE OXYGEN FROM SAID HEATING ZONE AND COMMINGLING IT WHILE STILL HOT WITH HIGHLY SUPERHEATED STEAM, INTRODUCING THE THUS COMMINGLED HIGH TEMPERATURE GASEOUS STREAMS AS SAID GASIFORM MIXTURE MAINLY COMPOSED OF CARBON DIOXIDE AND SUPERHEATED STEAM INTO CONTACT WITH THE PARTICLES IN SAID GAS PRODUCING ZONE, CONTINUOUSLY WITHDRAWING RESULTING HOT ASH PARTICLES FROM SAID BURNING ZONE AND PASSING THEM IN DIRECT HEAT EXCHANGE WITH AN AQUEOUS STREAM OF APPRECIABLY LOWER TEMPERATURE AND THEREBY COOLING SAID ASH PARTICLES AND PRODUCING A SEPARATE STREAM OF STEAM, AND PASSING SAID SEPARATE STREAM OF STEAM IN INDIRECT HEAT EXCHANGE RELATIONSHIP WITH AN OXYGEN-CONTAINING GAS STREAM BEING INTRODUCED TO SAID BURNING ZONE. 